1. Field of the Invention
This invention relates to an apparatus, including a product having a rigid sleeve, such as a steel sleeve, that can be integrated into a collapsible core or into a mold containing collapsible cores, for improved molding performance.
2. Discussion of Related Art
Collapsible cores in molding apparatuses and methods for molding plastic pieces or articles are known. Conventional collapsible cores often include a center core pin and a core sleeve positioned or mounted about the core pin. Some known collapsible cores have alternating non-collapsing segments secured to the center core pin and a same or corresponding number of uniform, alternating, sometimes arcuate, collapsing segments secured to the core sleeve. The relatively wide collapsible segments are movable or can be moved between the non-collapsed segments to form an expanded position for a molding operation, such as where the relatively wide segments are separated by the relatively narrower segments, and also to form a collapsed position where the collapsible segments are collapsed radially inward upon axial withdrawal of the center pin to form a generally cylindrical cross section, such as an arcuate area, to allow ejection of a molded plastic article from the mold.
This invention addresses and solves at least one common problem that can occur with collapsing cores. For example, a common mold sequence for collapsible cores, also known as c-cores, can have two stages. In a first stage, the c-core collapses, and then the molded part is ejected from the mold, such as by a stripper plate or other suitable ejection device. One problem can occur when or as the c-core is collapsing, because the plastic or molded part can or often does stick to one or more segments of the c-core. This sticking can cause or result in pinching the steel or can result in cuts from the steel on the molded part and thus can result in unacceptable damage to the molded part. In one embodiment according to this invention, this problem is addressed by adding a part retention feature to a retainer, sleeve and/or ring bolted directly to or with respect to the stripper plate.
The retainer or part retention feature of this invention can prevent the molded part from collapsing inward with the c-core. However, one problem with this type of part retention feature is that it needs to be sized large enough to retain the molded part but also simultaneously sized small enough to allow the molded part to eject from the mold, particularly after the core or c-core is collapsed or otherwise moved away from the molded part. It is sometimes difficult to achieve the delicate balance between the sizes so that the retainer or part retention feature provides or offers just enough resistance while simultaneously allowing for easy ejection of the molded part. For example, switching colors and/or running different grades of plastics or other materials can significantly impact this delicate balance in the manufacturing process. Quite often, it is eventually necessary to employ a robotic arm to support the molded part during ejection which results in slower cycle times and significantly increased costs. Another option to overcome this problem would be to change the mold design to a 3-stage ejection which can also add costs and design complexity to the mold.